OAuth2 implicit grant (token flow) does not work in IE/.Net Winform WebBrowser

For #1, I have no idea what's happening, but I can't see how it would be a Dropbox issue. It certainly doesn't happen in the code I shared earlier, so it also doesn't seem to be an issue with the WebBrowser control under its default settings.

For #2, I had a little trouble following what happens under what circumstances, but it doesn't sound like the expected behavior to me. What I would expect:

1. If already logged in, no login page is displayed (i.e. no email/password fields present).
2. Otherwise, the login page is displayed.

Regardless of which of those happened:

1. If the user has an existing active access token for the app, they're not asked to authorize the app again (no screen with "allow" button). Instead, they're automatically redirected to the redirect URI.
2. Otherwise, the user is asked to authorize the app (click the "allow" button). Only after doing that are they redirected to the redirect URI.

Does that match what you're seeing or not?